The effect of sex hormones on aortic collagen and elastin metabolism is being investigated in rats on (a) normal diet and (b) atherogenic diet. During the first phase of the project ovariectomized and intact female rats are being used and the effects of estradiol and contraceptive steroids are being studied. Measurements include (1) the synthesis and degradation of aortic collagen and elastin, (2) cholesterol, calcium, total connective tissue, and glycosaminoglycan content of aortas, and (3) histologic studies. Systolic blood pressure is measured in all rats. In the second phase of the project male rats will be studied in similar manner. The overall objective of the study is to determine the effect of sex hormones on vascular connective tissue and to relate these findings to the development of atherosclerosis in the animals.